1. Technical Field
The present invention relates generally to the field of computer architecture and, more specifically, to methods and systems for managing resources among multiple operating system images within a logically partitioned data processing system.
2. Description of Related Arts
A logical partitioning option (LPAR) within a data processing system (platform) allows multiple copies of a single operating system (OS) or multiple heterogeneous operating systems to be simultaneously run on a single data processing system platform. A partition, within which an operating system image runs, is assigned a non-overlapping sub-set of the platform's resources. These platform allocable resources include one or more architecturally distinct processors with their interrupt management area, regions of system memory, and I/O adapter bus slots. The partition's resources are represented by its own open firmware device tree to the OS image.
Each distinct OS or image of an OS running within the platform are protected from each other, such that software errors on one logical partition cannot affect the correct operation of any of the other partitions. This is provided by allocating a disjoint set of platform resources to be directly managed by each OS image and by providing mechanisms for ensuring that the various images can not control any resources that have not been allocated to it. Furthermore, software errors in the control of an OS's allocated resources are prevented from affecting the resources of any other image. Thus, each image of the OS (or each different OS) directly controls a distinct set of allocable resources within the platform.
A significant problem in an LPAR computer system is the mechanism that performs the isolation of partition resources from each other.
In some previous implementations, such as, for example, the IBM S/390, a product of the International Business Machines Corporation of Armonk, N.Y., the platform included extra hardware in each processor that added a fixed offset to all processor generated addressed. The added hardware also checked to make sure that the resulting address did not exceed a specific upper value. This extra hardware is made inaccessible to the logical partition's OSs. However, this method forces all the logical partition's directly accessible resources to be configured in a single (or at most a few) contiguous regions of the platform's address space. Other partition resources, such as, for example, sparsely mapped memory and mapped input/output (I/O) devices, must be accessed indirectly through platform firmware.
Another popular method, employed by Sun Micro-Systems, Inc., as well as Intel based systems, is to electrically disconnect, in some fashion, the bus between sub-sets to be configured with the complete set of resources that the partition needs. Thus, changing a partition's resource configuration often involves physically moving hardware between the sub-sets.
Therefore, it is desirable to have a method, system, and apparatus that isolates partition resources from each other while allowing fine grain allocation of resources to partitions without necessitating the physical movement of the hardware during reconfiguration.